Clutch/brake mechanism

ABSTRACT

A commuter wheel is mounted on a threaded shaft between two pulleys. The pulleys are free to rotate on the shaft but are braced against movement along the axis of the shaft. The direction of shaft rotation determines which pulley is driven by the commuter wheel. The device is used to wind and rewind a tape between two spools.

United States Patent Inventor Raymond K. Egnaczak Williamson, N.Y.837,144

June 27, 1969 Nov. 30, 1971 Xerox Corporation Rochester, N.Y.

Appl. No. Filed Patented Assignee CLUTCH/BRAKE MECHANISM 1 Claim, 5Drawing Figs.

U.S. Cl 242/201,

242/67.4 Int. Cl ..G11b 15/30 Field of Search 242/201,

[56] References Cited UNITED STATES PATENTS 2,012,437 8/1935 Segal242/67.4 2,675,974 4/1954 Jones... 242/205 3,495,789 2/1970 Gerfast242/20l FOREIGN PATENTS 822,446 1 1/195l Germany 242/201 PrimaryExaminer-George F. Mautz Auomeys-James J. Ralabate, Michael H. Shanahanand David C. Petre ABSTRACT: A commuter wheel is mounted on a threadedshaft between two pulleys. The pulleys are free to rotate on the shaftbut are braced against movement along the axis of the shaft. Thedirection of shaft rotation determines which pulley is driven by thecommuter wheel. The device is used to wind and rewind a tape between twospools.

PATENTEDuuvaman 35235 0 INVENTOR. RAYMOND K. EGNACZAK ATTORNEYBACKGROUND OF THE INVENTION This invention relates generally to drivemechanisms and in particular to a novel clutch/brake device for a webwind and rewind mechanism.

In a web wind and rewind mechanism, a web (such as paper tape, magnetictape, or cellulose film) is dispensed from a wind spool and taken up ona rewind spool. Heretofore, the repeated feeding of a web from one spoolto another has required a complex array of gears and levers. Theproblems adding to the complexity of the drive system include theproblem of switching power from one spool to the other. A critical partof this switching operation is the application of power to one spoolsubstantially simultaneously with the removal of the power from theother. This simultaneous application and removal of power is desirablein order to prevent the exertion of excessive tensions on the web.

Accordingly, it is an object of this invention to overcome the abovenoted disadvantages. Specifically, it is an object of the presentinvention to devise a drive mechanism capable of transmitting the energyof a power shaft to a load member in response to the direction ofrotation of the power shaft. Furthermore, it is an object of theinvention to devise an improved and simplified web wind and rewindmechanism.

Another object of the present invention is to devise a clutch/brakemechanism engageable and releasable by the direction in which a shaft isrotating.

Even a further object of this invention is to devise means forincreasing the mechanical couple between a clutch/brake and shaft inresponse to an increase in the load on the clutch/brake.

These and other objects of the present invention are accomplished bymounting a commuter wheel on a drive shaft between two pulleys. Thepulleys or load members are mounted on the shaft in a manner permittingthem to rotate freely relative to the shaft while being held againstsliding movement along the axis of the shaft. The commuter wheel on theother hand is designed to slide along the shaft between the pulleys inaddition to rotating with the shaft. The commuter wheel is internallygrooved to mate with a pin or thread on the shaft. The commuter wheel istherefore a direction sensing member that not only rotates with theshaft but also moves back and forth along its axis as the shaft isswitched between clockwise and counterclockwise rotation. The commuterwheel transmits the energy of the shaft to one or the other pulleys bymoving into mechanical engagement with the pulley. The direction ofshaft rotation determines the direction in which the commuter wheelmoves along the shaft and therefore determines whether a particularpulley is engaged or released. In the web wind and rewind mechanism thedirection sensing drive mechanism powers the rewind spool to feed outthe web, releases the rewind spool for gentle braking when the powershaft is stopped and smoothly couples the wind spool to the power shaftwhen the direction of shaft rotation is reversed. At no time during thisoperation is excessive tension exerted on the web. To the contrary, thepresent drive mechanism offers foolproof protection for the web andthereby permits the web to be rapidly and safely switched between windand rewind directions of travel.

DESCRIPTIONS OF THE DRAWINGS Other advantages and features of thepresent invention will become apparent upon consideration of thedetailed disclosure of the invention especially when taken inconjunction with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of a web wind-rewind mechanismemploying the present direction sensitive clutch/brake device;

FIG. 2 is a sectional view of the clutch/brake device taken through theaxis of rotation of the power shaft;

FIG. 3 is an isolated, perspective view of a section of the clutch/brakecommuter wheel; and

FIG. 4a and b schematically illustrate the operation of the clutch/brakemechanism.

DESCRIPTION OF THE INVENTION A web wind-rewind mechanism is shown inFIG. 1 with the web 1 being anchored by appropriate means at one end tothe wind spool 2 and at another end to the rewind spool 3. The spools 2and 3 are reels or bobbins between which the web I is wound and rewound.The spools 2 and 3 are coupled to the wind and rewind shafts 4 and 5respectively which in turn are coupled to the wind and rewind pulleys 7and 8. Power is transmitted to either the wind or rewind pulleys fromthe motor 9 through the direction sensing drive mechanism orclutch/brake 10.

The clutch/brake 10 includes the power shaft 12, the two load pulleys l3and 14 and the commuter wheel 15. The commuter wheel is a directionsensing member mounted on the power shaft to rotate with the shaft andto slide back and forth along its axis 17 in response to clockwise andcounterclockwise rotation of the power shaft 12.

The output pulleys 13a and 14a are rigidly connected to the load pulleysl3 and 14 by means of the collars 13b and 14b and the sleeves 13c and140. The collars are rigidly connected to the load pulleys by set screwsor other appropriate means and are rigidly connected to the outputpulleys by the sleeves. The sleeves have diameters larger than shaft 12and are slidably fit over the shaft. Each sleeve is welded or otherwiserigidly connected between an output pulley and a collar. The outputpulleys are joumaled for rotation on shaft 12 by appropriate bearings topermit them to rotate with the load pulleys relative to the shaft.

The clutch/brake 10 is coupled to the wind pulley 7 by the continuousbelt 18 looped over the wind pulley and the output pulley 13a. Likewise,the mechanism 10 is coupled to the rewind pulley 8 by the continuousbelt 19 looped over the output pulley 14a and the rewind pulley 8. Thepower shaft I2 is coupled directly to the motor 9 by appropriate means.

The motor 9 is a mechanical energy source for rotating the power shaft12 and may be any suitable driving device or mechanism. Preferably, themotor 9 is a shunt wound DC electric motor. The armature of the motor 9is connected directly to the power shaft 12 and is capable of beingdynamically braked and rapidly reversed in direction of rotation.

Turning now to FIG. 2, the load pulleys l3 and 14 are journaled forrotation on shaft 12 by the bearings 21 and 22. The bearings andtherefore the load pulleys are braced against movement along the axis 17of the shaft 12 by the retaining rings 23 (at four places). Therefore,the load pulleys l3 and 14 can rotate relative to shaft I2 and arelocked against movement along the axis of the shaft.

The load pulleys l3 and 14 have the angled flanges 24 and 25respectively which are sloped in the direction of the axis 17 toward oneanother at substantially the same angle. The commuter wheel 15 ismounted on the shaft 12 between the flanges 24 and 25. Thecross-sectional view of the commuter wheel in FIGS. 2 and 3 reveal itsmetal rim 26a and the tire 26.

The surfaces 27 and 28 of the tire portion 26 are sloped at an anglesubstantially equal to or greater than the angle defining the slope ofthe flanges 24 and 25.

Surfaces 27 and 28 are friction surfaces designed to frictionally engagethe sloped flanges 24 and 25 and thereby rotate the load pulleys withthe commuter wheel. Obviously, the commuter wheel engages only one loadpulley at a time. The slopes chosen for the flanges and the frictionsurfaces are intended to increase the mechanical engagement between thecommuter wheel and load pulley. First of all, the commuter wheel 15 iscaused to move against a flange of a load pulley because of the rotationof the shaft 12. As the rotational speed of shaft 12 is increased, theforce between the load pulley and the commuter wheel is increased. Inaddition, the slopes of the flange and of the friction surfaces increasethe mechanical engagement between the commuter wheel and load pulleyeven more. The sloped friction surface is a wedge which behavessimilarly to a doorstop slipped under the crack of a door to keep itfrom shutting. Consequently, the harder the friction surface is forcedagainst a flange the greater becomes the mechanical couple between thecommuter wheel and the load pulley.

Commuter wheel is coupled to the power shaft 12 by the pin or thread 29.The pin 29 is fit into the slot 31 drilled through the shaft 12 andprotrudes beyond the shaft on both sides. The rim portion 26a of thewheel has two grooves 32 positioned 180 apart on the inside of the rim26a which mate with the two protruding ends of pin 29. The grooves aregenerally helical and are skewed relative to the axis 17. When the shaft12 is rotated the pin 29 not only rotates wheel 15 but also displacesthe wheel along the axis of the shaft. The grooves 32 and the pin 29effectively make the commuter wheel 15 and shaft 12 functionallyequivalent to a nut and bolt. The wheel is like a nut in that it has aspiral or helical groove and the shaft is like a screw in that it has athread, i.e. the pin. Clockwise and counterclockwise rotation of theshaft (the screw) causes the wheel (the nut) to advance back and forthalong the length of the screw.

FIGS. 4a and b illustrate the forces causing the commuter wheel torotate and'translate along the axis of the shaft 12. The pin 29 isinserted into groove 32 and exerts a force on the wheel in the directionof shaft rotation thereby rotating the wheel with the shaft. The slopeor pitch of the groove 32 relative to the axis 17 gives rise to a forcecomponent parallel to the axis 17 that translates the wheel along theaxis. The parallel force component causes the wheel to move along theaxis 17 in a direction determined by the slope of the groove 32 relativeto the direction of rotation. The rotation direction indicated by arrow34 and the slope or pitch of the groove 32 indicated by angle C causethe wheel 15 to move to the left as indicated by the arrow 36. In thecase described, the wheel is caused to engage the load pulley 13 therebywinding web 1 from spool 3 onto spool 2.

The operation of the web wind and rewind mechanism of PK 1 begins byenergizing motor 9. The armature of the motor 9 is rotatedcounterclockwise to wind the web from spool 3 onto spool 2. The motorimparts a counterclockwise rotation to the power shaft 12 causing thecommuter wheel to move toward and engage the load pulley 13. The loadpulley t3, the collar 13b, sleeve 13c, output pulley 13a and belt 18transmit the energy of the motor to the wind pulley 7, wind shaft 4, andultimately spool 3. An operator action stops the motor 9 causing theshaft 12 to decelerate. The deceleration of the shaft 12 initiates theseparation of the commuter wheel friction surface 27 from the flange 24thereby removing the driving power of motor 9 from the load pulley 13.The commuter wheel begins a definite movement toward the load pulley 14when the shaft is rotated in the clockwise direction.

The commuter wheel friction surface 28 engages flange 25 to rotate theload pulley l4, and thereby drive collar 14)), sleeve l4c, output pulley14a, belt 19, pulley 8, shaft 5 and ultimately rewind spool 3.Consequently. the web 1 is fed from spool 2 onto spool 3. Subsequentchanges in the direction of rotation of shaft 12 efiect like changes inthe direction of the web 1 back and forth between the spools 2 and 3.

The clutch/brake mechanism 10 can be readily adapted to machines otherthan the wind-rewind mechanism of FIG. 1. Only one load pulley orsimilar member need be employed in the clutch/brake since the engagementof each load pulley is dependent on a particular direction of shaftrotation. The relative position of the load pulley and commuter wheelcan be interchanged such that the pulleys move in and out of engagementwith a stationary commuter wheel rather than vice versa. Also, the shaftcan be grooved rather than threaded and the commuter wheel threadedrather than grooved. The name clutch/brake is given to the devise 10because the selective engagement of the load pulleys to the power shaftcan be arranged to brake a load rather than power it. The foregoingremarks and observations make it apparent that modifications can be madeto the present invention without departing from the spirit or scopethereof.

What is claimed is:

l. in a web wind-rewind mechanism wherein mechanical energy isalternately coupled to first and second spools between which a web iswound back and forth, the improvement being a direction sensing drivemechanism for alternately coupling mechanical energy to a spoolcomprising a shaft supported for rotation and for coupling to amechanical energy source,

first and second load pulleys coupled to said first and second spoolsrespectively, journaled for rotation on said shaft, locked againstmovement along the shaft axis of rotation and having conically shapedflanges sloped toward one another at substantially equal angles relativeto said shaft axis, and

a commuter wheel mounted over the shaft between the first and secondpulleys including a rim having a helical groove mated with a threadmember on the shaft for rotating the wheel and moving it along saidshaft axis toward the first pulley when the shaft is rotated clockwiseand toward the second pulley when rotated counterclockwise and areplaceable rigidly mounted around the rim having first and secondconically shaped friction surfaces facing the sloped flanges on saidfirst and second pulleys respectively, sloped at angles relative to saidshaft axis equal to or greater than the angle at which an adjacentflange is sloped for enabling a friction surface to drivingly couplerotation of said shaft to a pulley and spool.

1. In a web wind-rewind mechanism wherein mechanical energy isalternately coupled to first and second spools between which a web iswound back and forth, the improvement being a direction sensing drivemechanism for alternately coupling mechanical energy to a spoolcomprising a shaft supported for rotation and for coupling to amechanical energy source, first and second load pulleys coupled to saidfirst and second spools respectively, journaled for rotation on saidshaft, locked against movement along the shaft axis of rotation andhaving conically shaped flanges sloped toward one another atsubstantially equal angles relative to said shaft axis, and a commuterwheel mounted over the shaft between the first and second pulleysincluding a rim having a helical groove mated with a thread member onthe shaft for rotating the wheel and moving it along said shaft axistoward the first pulley when the shaft is rotated clockwise and towardthe second pulley when rotated counterclockwise and a replaceablerigidly mounted around the rim having first and second conically shapedfriction surfaces facing the sloped flanges on said first and secondpulleys respectively, sloped at angles relative to said shaft axis equalto or greater than the angle at which an adjacent flange is sloped forenabling a friction surface to drivingly couple rotation of said shaftto a pulley and spool.